1. Field of the Invention
The subject invention generally pertains to doors and more specifically to a door panel with extruded panel members.
2. Description of Related Art
Almost any type of door can be struck by a vehicle either intentionally or by accident. However, some doors can withstand an impact better than others. For example, impact doors are freely swinging doors that are opened by intentionally striking and pushing the door open with a vehicle, such as a forklift or other type of material handling equipment. Impact doors are usually made of particularly tough materials to endure repeated hits. Such doors are also preferably as light as possible to minimize inertial forces that develop during impact. Unfortunately, reducing a door's weight without sacrificing its toughness can be difficult to achieve.
Sectional doors are also susceptible to being struck by a vehicle, although in this case the collisions are usually unintentional. A sectional door typically includes a series of panels whose adjacent horizontal edges are each pivotally connected by a row of hinges. As the door opens or closes, the door panels travel along two lateral tracks that in one configuration curve between horizontal and vertical. To close the door, the tracks guide the panels to a vertical position. When the door opens, the hinges allow the panels to curve around onto horizontal sections of the tracks, where the door panels store horizontally overhead. In other configurations, the sectional door maintains a generally vertical, planar configuration and is stored more directly above the doorway. Such doors, regardless of their configuration, can be powered up or down or can be manually operated. To ease the operation of the door, a torsion spring is often used to offset the weight of the door panels. Sectional doors are commonly used as residential garage doors; however, they are also often used in warehouses and other industrial buildings.
When used in high-traffic industrial applications, sectional doors are very susceptible to being struck by large trucks, trailers, forklifts and other vehicles. Collisions are often caused by a door's torsion spring becoming weak with age or not being properly preloaded, which can allow a door to droop into the doorway by not opening fully. Consequently, an upper edge of a vehicle may catch the lowest panel of the door, which often breaks or destroys just that panel.
To avoid having to repeatedly replace the lowest panel with an identical one (or indeed any panel on a door, as panels beside the lower-most one get damaged), a more impact-resistant panel can be used as a replacement, such as a panel that is tougher and more flexible. However, to do so, the replacement panel should be about the same size as the one being replaced. The replacement panel should also have a seal member whose shape and location is suitable for sealing against an existing door panel. Providing such a replacement door panel can be difficult to do, because of the different types of seals and the wide range of existing door panel sizes. A panel design whose length, width or seal configuration is riot readily altered would generally require a large inventory of panels to meet the requirements of numerous door applications.
Some door panels have metal frames with sheet metal skins. Such construction features can make a door panel difficult to shorten or lengthen (along the width of the doorway) to match the existing panels. Such features also make it difficult to change a door panel's width (vertical dimension when the door is closed).
Other door panels may perhaps be extruded, such as those of U.S. Pat. Nos. 5,718,276; 5,445,206; 5,170,832; 4,979,553; 4,924,932; 4,432,591 and 3,247,637. Extruded panels may be relatively easy to cut to length (i.e., doorway width); however, their width and seal geometry is generally fixed. It's conceivable that interconnecting a series of relatively narrow panels could create doors and/or individual panels having various accumulated heights. However, with current designs, flexing between each adjacent panel means each individual panel may need to have its own means for guiding itself along the track. Since each additional guide member contributes drag to the door's movement, a door with numerous narrow panels may be more difficult to open and close than a door with fewer panels. The problem of drag not only applies to doors whose bottom panel is replaced, but also applies to all doors including new door construction.
Consequently, there is a need to be able to manufacture replacement door panels as well as entire doors for doorways of various width and height, and to be able to do so without having to manufacture and stock numerous door panels of various sizes and seal geometries.
In addition, most current sectional door panels share the feature of having a monolithic design. For example, a common design of such a monolithic panel is a formed metal “pan” with a fairly complex profile, and to which hinges and roller hardware are attached. Other examples of a monolithic design are panels with a rigid frame structure and including filler material within the frame and facing panels on the exterior surfaces. Yet, another example is found in U.S. Pat. No. 2,951,533, which discloses a panel comprised of glued-together components (see col 4, lines 17–23 of the patent). Because of such monolithic designs, damage to any given portion of such a panel (particularly damage that would negatively impact the operability of the door) requires replacement of the entire panel. There is currently not a practical way to be able to replace only a damaged section of an individual panel, as opposed to the entire panel itself.
The monolithic nature of current panels also prevents the possibility of being able to easily provide variability of material properties within a given panel, as may be advantageous depending on the application for the panel. For example, it may be that in a given application, a particular area of the panel (illustratively, the lowermost third) is more susceptible to impact. In such an application, it would be desirable for that area of the panel to be more resistant to impact than the rest of the panel, without having to form the entire panel out of the (typically more expensive) impact-resistant material. For a monolithic panel, this could only be achieved by adding material or structure to the panel in that particular area. A more flexible approach would be to provide for a non-monolithic design wherein the desired material property for a given area of the panel could be easily provided and preferably easily modified according to the application.